1. Field of the Invention
This invention pertains to the field of self-wound covering materials using a laminate with improved dimensional stability. More particularly, this invention relates to improved decorative or protective laminates comprising a substrate which under normal processing conditions, i.e., printing of indicia, becomes dimensionally unstable, wherein the dimensional stability is improved by incorporating a stabilizing layer or layers of polymer films to reduce or eliminate shrinkage, edge curl and distortion of printed indicia after application to a substrate, e.g., walls or shelves, for decorative and/or protective purposes.
2. Description of the Prior Art
Self-wound and non-self-wound covering materials are used in a great variety of areas, such as, for tapes, decals, decorative and protective coverings in sheet form for walls, furniture, and the like, self-stick floor coverings, and generally, for any purpose wherein it is desired to adhere an article to a substrate. Self-winding is more desirable in that it eliminates the need to strip and discard a protective release layer as part of the application process.
Commonly-owned U.S. Pat. No. 4,151,319, Sackoff et al., granted Apr. 24, 1979, discloses methods of making both strippable non-self-wound and self-wound pressure sensitive adhesive coated laminates. The methods involve application of a modified pressure sensitive adhesive layer containing means for decreasing the zero-minute peel value of the facing layer-pressure sensitive adhesive layer of the laminate. This is accomplished by mixing a specifically selected polysiloxane into the pressure sensitive adhesive and such a modification of the pressure sensitive adhesive yields products which may be repositioned during application without tearing, stretching or otherwise causing damage. Special mention is made of the specific teaching in Sackoff et al. at Col. 6, lines 48-54, in which a self-wound construction having a release coated outer facing layer is used with the modified pressure sensitive adhesive. Also of special interest in this connection is the disclosure in commonly-owned pending application of Smith, U.S. Ser. No. 08/043,388, filed Apr. 6, 1993. Smith discloses an improved modified pressure sensitive adhesive for use in the laminates of the type described by Sackoff et al. Smith employs a mixture of specific silicones as a zero peel strength modifying means and their use in self-wound self-adhesive laminates wherein the outer surface of a facing layer possesses improved release properties.
Sackoff et al. and Smith disclose that a desirable feature of a preferred embodiment of their invention is to produce a so-called self-wound surface covering, i.e., one which does not use or require a protective temporary release sheet which must be removed and discarded as part of the application process. However, each specifically state (e.g. Sackoff et al., Col. 4, lines 55-60) that such embodiments are uniquely useful for narrow tapes, thus teaching away from the use of self wound rolls in widths suitable for covering walls, shelves and the like with rolls wider than for example those used in tapes or borders. While the reasons for such preferences are not clearly understood at this time, it is believed that unwinding larger rolls made in accordance with the mentioned prior art will cause delamination and damage to the outer surface because of failure to release along the longer contact lines.
Although the surface coverings provided by Sackoff et al. and by Smith's teachings have enjoyed wide commercial acceptance, especially in the case of using strippable layers for protecting the adhesive prior to application, the self-wound embodiments have several shortcomings. If, for example, a vinyl substrate is used, normal processing operations, such as in-line printing or adhesive coating, can cause distortions in the substrate. These can lead to dimensional stretching, which is unrelieved during winding, and usually is not noticed until after application. Such distortions tend to relieve themselves after application whereupon any printed indicia can be distorted itself, and edge lifting or edge curl might be seen. Adhesives with high peel strength values have been utilized to reduce these affects, however using these adhesives will make the surface coverings difficult to remove in the long run resulting in damage to the substrate, e.g., painted wall board, upon removal.
It has now been discovered that providing such laminates which further incorporate one or more polymeric layers selected to remain dimensionally stable under normal processing conditions overcomes all of the drawbacks of the self-wound surface coverings of the prior art. Specifically, the dimensionally stable surface covering will not exhibit the defects of the prior art upon application. Also, the surface coverings of the current invention show improved stain resistance and can be removed after years of service without damaging the substrate since there is no need to use an adhesive with excessively high peel strength values.